Turbocharger systems increase the power and efficiency of internal combustion engines by providing the engine with intake fluid at higher than atmospheric pressure. Conventional turbocharger systems include a turbine driven by exhaust energy from the engine, and a compressor driven by the turbine. The compressor pressurizes fluid, previously at or near atmospheric pressure, for travel through a throttle valve and aftercooler and into an engine intake manifold.
Controlling the turbocharger system to obtain desired engine operation has been a difficult problem. Under certain conditions, the driving speed of the compressor and intake fluid pressure can cause excessive compressor output, resulting in a compressor choke condition. When the compressor is operating in a choke condition, the fluid flow through the compressor is unsteady, characterized by fluid pulses followed by periods of interrupted fluid flow. Compressor choke decreases the efficiency and capability of the turbocharger system, which reduces the stability of the engine.
Under certain other conditions of the turbocharger system, the driving speed of the compressor and the pressure of the intake fluid can cause the compressor blade to rotate at speeds causing the intake fluid to separate from the compressor blade. This condition is known as compressor surge and results in high overspeeding of the compressor. Light compressor surge decreases the efficiency and capability of the turbocharger system, which reduces the stability of the engine. Hard compressor surge conditions can result in a relatively quick catastrophic failure of the turbocharger system.
U.S. Pat. No. 5,694,899 to Chvatal et al. attempts to eliminate the occurrence of compressor surge in a turbocharger system by providing a controlled bypass line connecting the turbocharger's compressor outlet line to the compressor inlet line. When the bypass line is opened, the mass flow rate of gas flowing through the compressor is increased and the pressure downstream of the compressor is reduced. The increase in mass flow rate of the gas and reduction in downstream pressure serves to avoid the surge condition. The disclosure of Chvatal et al., however, does not describe how the operating condition of the compressor is monitored to determine when the compressor is in a surge condition, or in danger of being in a surge condition, and thus when it is appropriate to open the bypass line.
Other conventional turbocharger systems determine the operating condition of the compressor by measuring various operational characteristics of the turbocharger system and engine, calculating a mass flow rate of fluid through the compressor, and comparing the measured and calculated values against a turbocharger control map. The turbocharger control map identifies, for example, when a surge condition will exist based on known values for a pressure ratio of the compressor and a mass flow of the compressor.
These conventional methods for determining the operating condition of a turbocharger system, however, are prone to inaccuracy due to the numerous measured values and equations required to determine the mass flow rate of a compressor. Further, such methods do not adequately compensate for atmospheric pressure variations among work sites.
The present invention provides a turbocharger control management system that avoids some or all of the aforesaid shortcomings in the prior art.